Prepare Mg SR2 release

Prepare the Magnesium SR2 release that is Isofunctional with the master branch

This means to:

• cherry-pick related bug corrections from master , functions such as OTN and T-API are particularly concerned
• update project version in poms
• update dependencies if needed (mostly odlparent versions)

            https://docs.opendaylight.org/projects/integration-distribution/en/stable-magnesium/platform-versions.html

• update others environment parameters e.g. for lighty.io and tox if needed (normally not)

Once that done, the release must be staged in Jenkins and then officially released using the self-service process

https://docs.opendaylight.org/en/stable-magnesium/release-process/project-release.html

This last task can only be performed when all upstreams dep are ready i.e. when all managed projects have been released (prevision date 27/7/2020).
The deadline is one week after all managed projects have been released.

Evaluation indicators:

• cherry-picks from master done
• magnesium stage release job OK in Jenkins
• tpce artifacts published on nexus